Clean-up crews on the shore of Lake Michigan near a BP refinery in Whiting, Ind.

Petty Officer 3rd Class Parker WoodU.S. Coast Guard

This post was updated as we waited for an estimate on how much oil spilled into Lake Michigan from the BP refinery in Whiting, Indiana. Now that an estimate has been released, we'll continue to follow this story in other posts.

Update: Thursday, March 27, 4:39 p.m.

BP has revised its estimate of how much oil spilled Monday. It now says 15-39 barrels leaked from the Whiting Refinery. That'sabout 630-1,638 gallons.

Petty Officer Jeremy Thomas is with the U.S. Coast Guard’s Marine Safety unit in Chicago.

He says a small crew has been removing the oil manually. He says the cleanup efforts are going well.

“That involves either a gloved hand or a shovel or rake or some sort of hand powered tool to remove the oil from the shoreline,” Thomas said.

Thomas says federal agencies are waiting for weather conditions to improve before assessing if there’s any heavy tar sands oil on the lake bottom.

“There’s nothing that leads us to believe that there’s any down there but we want to rule it out because of course we want to make sure the environment’s safe and healthy and clean,” Thomas said.

It’s not clear what exactly caused the spill or how long cleanup will take.

Update: Tuesday, March 26, 7:21 p.m.

BP released a statement about an hour ago saying they are still estimating the amount of oil that was spilled and assessing whether more work will need to be done. From their statement:

Crews have recovered the vast majority of oil that had been visible on the surface of a cove-like area of Lake Michigan and on the shoreline between the refinery and a nearby steel mill. They have used vacuum trucks and absorbent boom to contain and clean up the surface oil. Responders also manually collected oil that had reached the shore.

Monitoring continues in coordination with the U.S. Coast Guard, EPA and the Indiana Department of Environmental Management.

Update: Tuesday, March 26, 4:37 p.m.

Michigan Radio's Cynthia Canty spoke with Chicago Tribune environmental reporter Michael Hawthorne this afternoon about the spill. You can listen to the full interview here.

Hawthorne told us about the history of the Whiting refinery. It's one of the oldest refineries in the country.

"We don't know yet just how much oil was released from the refinery into Lake Michigan a couple of days ago. Some people were suggesting, at least off the record from the company, were suggesting that it was about 10 barrels - 12 barrels, not a lot in relative terms," said Hawthorne.

"And given the amount of pollution that's already going into the lake from that part of northwest Indiana, how much affect it had on the lake, at least in the eyes of environmental regulators is fairly minimal."

Just how the oil got into the cooling system is still a mystery. BP told us that the system is designed to keep the water and oil separate - similar to how the cooling system works in your car. Somehow, a slug of oil got into that cooling system.

... the BP Whiting refinery is one of the biggest industrial polluters on Lake Michigan.

The BP Whiting refinery recently completed an upgrade that cost nearly $4 billion so the facility could process heavier Canadian tar sands oil. The switchover meant the refinery needed permits that would allow more pollution to be released into the environment.

Hawthorne points out that the BP Whiting refinery is one of the biggest industrial polluters on Lake Michigan.

Update: Tuesday, March 26, 1:20 p.m.

The Chicago Tribune released this video of the cleanup along the shore of Lake Michigan. A BP refinery in Whiting, Indiana spilled a mix of heavy and light crude oil into the Lake. The EPA and the U.S. Coast Guard are overseeing the cleanup.

Update: Tuesday, March 26, 11:06 a.m.

We're waiting for an estimate on how much oil spilled into Lake Michigan from the BP refinery in Whiting, Indiana. BP spokesman Scott Dean said they expect to have that update later this afternoon. He says they base their estimate on how much oil they pull out of the water.

Dean said the winds on Lake Michigan have been blowing onshore, which kept the oil contained within the cove, and that they know of no wildlife impacts thus far.

BP says the oil that spilled was a mix of light and heavy crude oil.

Update: Tuesday, March 26, 8:50 p.m.

BP sent an update this evening saying the investigation into the spill continues as does the clean-up effort:

Lines of boom have been deployed to contain the oil and wind has blown oil toward the shore, where crews are vacuuming it out of the water and cleaning the limited quantities that have reached land between the refinery’s wastewater treatment plant and a nearby steel mill.

BP has not yet determined precisely how much oil was discharged but expects to be able to provide an estimate as early as Wednesday.

Original post: Tuesday, March 26, 5:07 p.m.

A BP spokesperson told us they don't have an estimate on how much crude oil spilled, but he says the spill has stopped and "the response remains underway."

The spill started sometime yesterday and was stopped around 1 a.m. this morning, according to Michael Hawthorne of the Chicago Tribune.

BP's Whiting refinery is located on the shores of Lake Michigan in northwest Indiana. See the red pin below:

The Coast Guard received a report Monday night from watchstanders the National Response Center of a sheen from an unknown substance discharging from an outflow adjacent to the refinery.

Personnel from Coast Guard Marine Safety Unit Chicago and the EPA responded last night and found an area of about 5,000 square feet covered in crude oil.

Oil booms and vacuum trucks are being used by BP in an attempt to clean up the spill. The Coast Guard reports that pollution responders found tar balls less than one centimeter in diameter on the shore of the cove, "averaging 20 tar balls per 10 feet of shoreline."

BP spokesman Scott Dean told the Associated Press that a malfunction led to the release:

He says the oil entered the refinery's cooling water system, which discharges into the lake about 20 miles southeast of downtown Chicago.

Indiana Department of Environmental Management spokesman Dan Goldblatt says an agency staffer reported seeing a large sheen on the lake about 2 a.m. Tuesday. Dean says that sheen was in the cove and was no longer visible several hours later.

The refinery processes heavy diluted bitumen oil known as "tar sands" oil. That type of oil can sink in turbulent water making cleanup more difficult.

BP says they will have an update later this evening. The U.S. Coast Guard and the U.S. EPA are overseeing the cleanup.